Image sensors are widely used in various imaging applications and products, such as cameras, scanners, photocopiers, etc. A performance of an image sensor is depended on a dark current.
The dark current occurs when some electric current flows through the image sensor even no photons are entering the image sensor. The dark current is one of sources for noise in the image sensors. The dark current is referred to as a leakage current in non-optical devices such as in transistors.